Tunable Small-Angle Nonreciprocal Radiation and Broadband Absorption in a GST-Weyl Semimetal Resonant Structure

Nonreciprocal radiation is essential for advanced thermal photonics but is constrained by static performance and large incident angle requirements in current Weyl semimetal (WSM)-based devices. Here, we propose a WSM-Ge2Sb2Te5 (GST) hybrid resonant structure to achieve thermally tunable dual functionality. When GST is amorphous, the structure exhibits strong small-angle (5{degree sign}) nonreciprocal radiation at 14.09 μm, with a nonreciprocity coefficient of up to 0.95, driven by coupled guided-mode and Fabry-Perot resonance. Upon annealing, GST transforms to the crystalline state, enabling broadband high absorption across 12-15 μm with reciprocal behavior. Structural parameters modulate the resonant wavelength by adjusting the effective refractive index or optical path, while GST crystallinity significantly regulates nonreciprocal performance. This non-volatile design overcomes key limitations of static nonreciprocal devices, holding promise for adaptive energy harvesting and intelligent electromagnetic protection.